A region of circuitry may be isolated to save power. For example, a switch may be used to connect a power supply to the region when the region is used, but disconnects the region when it is not used. Thus, a virtual power grid may be formed at one end of the switch, whereas the power supply may interface at the other end of the switch. The virtual power grid may remove problems associated with leakage in various components of the region of circuitry as the power supply to the region is cut off when the region is not being used.
However, when the region is connected or reconnected to the power supply (e.g., the virtual power grid is turned on or formed), a rush current or huge amount of current may flow via the switch towards the region to fill capacitance of the region which has been drifted to ground. As a result, the rush current may cause a voltage drop in the power supply which is feeding the virtual power grid and, at the same time, which may be feeding other regions of circuitry. That is, the rush current can cause a voltage drop in the other regions of circuitry which may make them fail. Furthermore, the rush current may cause an electro-migration problem in the virtual power grid, where the large current can eat away electrons in the virtual power grid, thus causing a breakage.